Tone and volume control



Dec. M, 1951 Filed Dec. 22, 1949 P. F. G. HOLST ETAL TONE AND VOLUME CONTROL 5 Sheets-Sheet 1 Dec. l1, 1951 P. F.' G. HOLST ETAL TONE AND VOLUME CONTROL.

5 Sheets-Sheet 2 7 am d ggz/wy Dec. ll, 1951 P. F, G. HoLsr x-:TAL 2,577,893

TONE AND VOLUME CONTROL Fglled Dec. 22, 1949 5 Sheets-Sheet 3 Q95 .119.42 .2&5 .55?. 6 VERY Louo Lcuo 1r-:mum s T I 75 77 5/75 77 fi? 7 75 BL A B B 79 7.9 7g

D] D /Lg J1 df Z :T de ze J- C C A A A PLUS MIDDLE MINUS A 95g a5 ZAWfljg A507 w 54 95 109 10,9 il a J'gjo f@ SYMPHONY e'wme son@ Patented Dec. 11, 1 951 UNITED ASTATES PATENT oFFlcE TONE AND VOLUME CONTROL Paul F. G. Holst and Morton J. Nelson, Cincinnati,

Ohio, assignors to Avco Manufacturing Corporation, Cincinnati, Ohio, a corporation of Dela- Ware Application December 22, 1949, Serial No. 134,384

23 Claims. (Cl. 178-44) directly in proportion thereto. Radio station operators ride the gain control so as to keep the transmitted variations produced by the sound level Within a certain range. When such signals are received by the radio receiver, no corresponding expansion or compression is provided. Furthermore, the reproduction usually is at a quite different level from the level of sound of the original source. According to the authority Fletcher, a change of the sound level of the reproduced sound, when compared with the original or normal level -of sound from the source', produces on the listener an eiect of an apparent change in tonal characteristic.

It, of course, is well known that individuals commonly set the volume control of a radio receiver at a particular value and then adjust the tone control in order to make the reproduction more pleasing and natural. The tone control provided by the average radio receiver, however, is incapable of providing sufficient compensation to overcome the apparent change in tonal characteristic, referred to by Fletcher. Even if a tone control were provided which could produce suicient compensation, the individual would encounter some diiculty in setting the tone control at the desired point depending upon the type of program being reproduced and the volume level desired for a particular occasion.

It, therefore, is apparent that it would be desirable to provide an improved tone and volume control Which could be adjusted in predetermined steps by a push button arrangement to provide the desired tone characteristic and the compensation required for any volume level of reproduction. Where no change in tonal characteristic is desired, so as to obtain a uniform reproduction, the predetermined steps of change of volume level are so compensated as to minimize the change in tonal LcharactersLic observed by the authority Fletcher.

In accordance with the present invention, an arrangement is provided whereby an adequate number of steps in volume change are provided by! means of a push button arrangement. For

those wishing certain control of the tone of reproduction, a push button arrangement is provided where again a predetermined performance characteristic can be obtained repeatedly whenever desired.

It is, therefore, an object of the present invention to provide an improved wide range tone control for sound reproducing circuits which is operated by push buttons.

Another object of the present invention is to provide a push button tone control which maintains the output level constant independent of the volume control setting.

Still another object of the present invention is to provide a push button volume control for compensation at the receiver for variations in audio sound level.

Other and further objects of the present invention subsequently will become apparent by reference to the following description taken in conjunction With the accompanying drawings where- Figure 1 is a block diagram illustrating the application of the present invention to a radio receiver;

Figure 2 is a circuit diagram illustrating the details of a push button volume and tone control;

Figures 3, 4, 5, and 6 are circuit diagrams illustrating the circuit arrangements provided when certain push buttons are actuated in the volume control bank;

Figures 7, 8, and 9 are circuit diagrams illustrating the intermediate volume control connections provided for any of the major volume control steps;

Figures 10, 1l, l2, and 13 are circuit diagrams illustrating the equivalent circuits provided by actuation of the major tone control push buttons; and

Figures 14, 15, 16, and 17 are graphical representations illustrating the reproduction characteristics obtained for different settings of volume and tone control.

The block diagram of Figure l shows the application of the present invention to a radio receiver of the superheterodyne type having a radio frequency amplier 2|, a mixer oscillator 22, an intermediate frequency amplifier 23 and an audio amplifier 24. Interposed between the second detector and the audio frequency amplifier 24 is a push button controlled circuit 25. In order to provide an optimum operation in accordance with the present invention, it is preferable to provide an improved or amplified automatic gain control voltage developed by virtue of the crystal 2`9-is fed by means of a conductor 3| tothe radio. fregueny amplifier and the mixer oscillatorgto 929.61196. th@ desired ampliiication characteristic.. Ita-will.` be..

noted that the push button control 25 is provided with I2 push buttons; 6 beingkfor .thecontrol of. the volume, and 6 being for'thecontrolfthe tone. The manner in which these pusii buttons control certain circuits isillustrated by the circuit diagram of Figure 2.

Four. push buttons 32, 33,y 34E and; 35, ppovide, A

4 major changes inthe volume` level, and for convenience, these have been labeled Very Loud,

Loud, Medium and Soft respectively, These.

switches are. so arranged thatwhen any one of the switches 32 to 35 is pressed, it releases the previously actuated switch. VThis type of switch construction is well known and old in, the art,

and a switch suitable for this purpose is manufactured by the Oak Manufacturing. Company of Chicago.

The first switch 32 for the very loud volurneis provided with 3 switch blades, 36, 31 and 38 whereasv the remaining volume push buttons are each provided with 2 switch blades. Thus, the Loud push button actuates switch blades 39 and 4|; the Medium push button, switch blades 42 and 43; and the Soft push button, switch blades 44 and 45. All of the switch blades in the circuit diagram are shown in a position prior to the actuation of any one of them, although subsequently it will becomeA apparent that the same effectis obtainedwhen the Medium push button has been actuated. Actuation of the various push buttons, 32 tol 35, controls a total variation in volume levelof` about 70 db,. so that Ythe 4four major steps are spaced aboutil db apart. In order to. provide a liner control of the volume, 2 additional push buttons 41. 'and'..; are provided which are labeled'Plus and'. Minus."

Push button 41 has 2 movable switch'blades" 49 and 5| whereas push button '|28` likewise. has 2 movable switch blades' 52and 59. T hus, foizactu'a-V tion of any particular one ofthe push buttons 32, to 35, actuation of the push button`41will in crease the volume levelby about 6 db. Actuation of the push button 48'will decrease the.' volume level predetermined by any of the push buttons' 32 to 35 by 6 db. When, however, theSoft push button 35 has been actuated, actuation of the Minus button 48 will reduce the volume Vlevel to 0.

The push buttons 41`andV 48 are so arranged that the actuation of any one of the major 'push buttons 32 to 35 produces a release of these buttons, but the actuation of either push button 41 orv 48 does not affect the position or condition of any of the push buttons 32 to 35.

Four major tonal change push buttons 54, 55, 58 and 51 are provided, which for convenience, have been labeled Speech, Song, Swing andSym.- phony. Each of these push buttons .has` 3 movable switch biadeps, and hencapush tuttgnsg will actuate switch blades 58, 59 and lil;` push button 55 will actuate switch blades 62, 6 3 and 64; push button 66 will actuate switch blades 65, |56l and 61; and push button 51 will actuate switch blades 68, 69 and 1|. Two additional push buttons, each having a single switch blade are provided, and these are labeled High Fidelity and Normal Fidelity. The push button 1 3.v labeled Normal Fidelity has a5 single switch blade," 13. which closes a. circiiit` between ground and an intermediate point in the audio 'frequency amplier. The High Fidelity push button 1,4 has a single switch blade 15 which, however, doesl not' produce any circuit changes in itself, but as soon as all of the push buttons 5 44 tor51, 12 andfr14 are so arranged that the actuation of; an! push button releases all of the remaining or previously actuated buttons, the push button 14. dees produce a circuit change.

conductor'16isconnected to receive audio frequency, from a suitable source, such as the detector of the radio receiver diagrammatically shownin Figure l, or from a.V phonograph pickup or`other source. The conductor 16 nectedl through a coupling capacitor 11'to` a voltagedividerformed of a plurality of resistors 18, 19,'8| and 82. The resistor. 82 is connected to a conductorv A which leads to the. Plusand Minusy push buttons. and from which a conductor 93- leads toa coupling. capacitor"84y which is connected to' the. grid of an. amplifier .tube 85. The output of. the ampliiiertubei is` provided througha resistor 89which is lay-passed to the cathode bythe capacitor 9|. The anode circuit of the tube-8 5. includes an anode resistory 92 which is4 connected to aisluitable sourceof po.-

tential. An r. f. by-pass capacitor 93 is connected between groundv andthe anode ofthe vacuum tube 85. The4 anode of the,l vacuum tube` 95 is coupled by a capacitor 94 to the grid.` of` the succeeding vacuum` tube 86 .which has a gridI circuit resistor 95. Connected to the anode-of the vacuum' tube 8 5,is another lay-pass capacitor 96 which isv connected -to oneof the` contacts of.` the normal switch 12which has its other contact.

connected to. ground. It, therefore, will be noted that the amount of. byrpasscapacitance pro- 'videdfor the. anodeofvacuum tube 85 may be complete a circuit from conductor 91l connected.

to the juncture of resistors. 811 and 82 `to conductor-98 which is connected. to oneterminal of thepushbutton` 33. The push button 33 in normal. position has its switch blade39 connected to the. conductor 98witha circuit. including a capacitor 99 and a resistor|9|` connected to ground. TheV switch. blade 31. of. the. push .button 32 normally is .in open. circuitposition but when. actuated will. completefa circuit. between.

conductorsz`|82t and: |03. which. respectively .are connected to` the 'junctures of. resistors4 191.'.and

8|- and. resistors. 18;` and 19. Theconductorili.

a conductorC which is connected to one :terminal of each of the pushbuttons 54, 55, 56..and 51.

When the switch blade 38jis actuated, thecon-A ductors 91;and, A are connected. togetheriso. as,v

'Ihersw'itchv blade 38 0f the.

to provide la short circuit or shunt across the resistor 82. l

, The switch blade 39, with the push button 33 innormal position, completes a circuit between the conductor 98 and the coupling capacitor 99 and the resistor which is connected to ground. The switch blade 4| of the push button 33 is normally in open circuit position and when actuated short circuits the resistor 82.

,The switch blades 42 and 43 of the push button 34 do not of themselves complete any additional circuits, but vthe actuation of this push button releases any previously actuated push button thereby to change the circuit to the vposition shown in solid lines in Figure 2.

The switch blade 44 of the push button 35 is in normal open circuit position, but when actuated connects the ground conductor to a conductor |04 which is ,connected to one terminal of thepush button 48 associated with the switch blade 53. The switch blade 45 of the push button 35 is in normal closed circuit position so as to interconnect the conductors |02 and 91 which short circuit or shunt the resistor 8 The switch blade 45 when actuated connects the conductor |02'to ground through a resistor |05 and a capacitr |06 so that this circuit is connected to the juncture` of resistors 19 and 8|. Reference may be made to Figures 3, 4, and 6 which show the various circuit arrangements provided upon actuation of the diierent push buttons 32, 33, 34 and 35. It will be recalled that conductor A goes to the push buttons 41 and 48 which provide the intermediate level steps, and hence, in these gures this portion of the circuit has been represented by the rectangle A. The conductor D from the juncture of the resistors 19 and 8| is connected to a plurality of series arranged capacitors normally connected through switch blade 69 of the tone control push button 51 to the conductor 16, and hence, this circuit combination has been shown by a rectangle D, on the assumption that for purposes of illustration the High Fidelity button 14 has been actuated. It thus becomes apparent that for the Medium position the juncture between the resistors 8| and 82 is connected to ground through coupling capacitor 99 and load resistor |0|. In the Soft position the juncture between the resistors 8| and 82 likewise has this same circuit arrangement, and in addition, the juncture between the resistors 19 and 8| is connected to ground through the capacitor |05 and the resistor |08. The manner in which com; pensation is introduced for the different volume levels in order to provide the proper tonal char- :acteristic subsequently will become apparent by reference to the performance curves shown in Figures 14 to 17.

The conductor A which leads to the Plus and Minus switches normally is connected to the switch blade 49 of the push button 41 to resistor |01 which is connected to resistor |08 which in turn is connected to resistor |09 having one terminal grounded. The switch blade 52 of the push button 48 normally Ishort circuits resistor |08. The juncture between the resistors |08 and |09 is connected to one terminal normally closed by the switch blade 5I of the push button 41 having its other terminal connected to the conductor 83. Actuation of the. push button 41, therefore, in eiTect connects the conductor A directly to the conductor 83. The push button 48 when actuated causes the switch blade 52 to open the shunt across the resistor |08 and to connect the juncture between Athe resistors l 08 and l 09 tol 4one ter- Medium button-34 of the volume control has been` minaljofthe.groundedresistor Il so that this` resistor isin parallel withresistor |09, The switch blade 53 of. the push `button 48 when actuated connects one terminal ofthe resistor to the conductor |04 which is connected to one terminal of the `normally open circuit connec tion of the switch blade 44 of the push button 35.

VReference will now be had to Figures 7, 8 and 9 which illustrate the circuit arrangements provided by actuation of the push buttons 41 and 48. Figure '1 shows that the conductor A is connected directly tothe conductor 83 so as to provide maximum energy transfer tothe vacuum tube 85 from the voltage divider .comprising the resistors 18, 19, 8| and 82, when button 41 is actuated. When neither of buttons i1 and 48 is actuated, the'circuit arrangement is that shown in Figure 8,

which shows thatv the resistors |81 and .|09 are effective. When the Minus button 48 has been actuated, the circuit arrangement is that shownv in Figure 9 showing that in addition to the resistors |81 and |88, resistors |08 and are connected in circuit.

The switch'blade 58 in normal position is in open circuit relationand when actuated, connects a grounded resistor ||2 to the conductor C. The switch blade 59 which normally is in open circuit condition, when actuated, connects the conductor 15 to conductor H3 which is vconnected to the juncture of capacitors H4 and H5. Capacitor ||4 is connected to conductor D which in eiect, therefore, connects the capacitor 4 to the juncture of resistors 19 and 8|. The switch blade 6| of the push button 54 also is in normal open oircuit position and when actuated connects a grounded resistor ||5 to conductor 16.

The ,switch blade 62 of the push button 55,h

when actuated, connects the conductor C to a circuit including a capacitor ||1, and a grounded resistor H8. The switch blade 63 when actuated interconnects the conductor 16 with the juncture between capacitors ||5 and ||8 so that the capacitors ||4 and ||5 are connected in series between the juncture of the resistors 19 and 8| and the conductor 16. The switch blade 54 of the push button 55 connects the conductor B from the juncture of the resistor 18 and 19 to a circuit i'ncluding a capacitor l2 and a grounded resistor 22.

The switch blade 65 of the push button 58 interconnects the conductor C with a circuit including a capacitor |23 and a grounded resistor |24. The switch blade 61 of the button 56 when actuated interconnects the conductor B from the juncture of resistor 18 and 19 to a circuit including a capacitor |25 and a grounded resistor |28.

The switch blade 68 of the push button 51 when actuated interconnects the conductor C with a circuit including a lcapacitor |21 and a resistor |28 which is grounded. 'Ihe switch blade 89 which is normally in closed circuit relation betueen the conductor 16 and a conductor |29 leading to the series capacitors ||9, I5 and H4 is opened when actuated. The switch blade 1| of the push button 51 when actuated completes a circuit between the conductor B and a circuit including a capacitor |3| and a grounded resistor |32.

Figure 10 illustrates the circuit arrangement provided when the Symphony button 51 has been actuated whereby therswitch blade 1| connects a'shunt circuit comprising the capacitor |3| and the resistor |32 between ground and the juncture oi ,the resistor,u 18 and 19. Assuming then the 51' connects "the'-circuiti-comprising? the' |28 a-ndl the capacitor-'|221 t--th conductor-A' ir' the eidterminal A'oii the'resistor 82.

vFigure ll--slfiiows therra'ng'erii'ei'it-` obtained` When-y push Vbit|o1``56 isituat'ed. 'Sitc'ethe' switch lblade 5'9 oflthe pushputtoxi 51 Yrintercorre nects the conductor 16 with the'series capacitors I I9; 'I |5- and 'Ifl l; thiscii'fcitiis' in efloctlb'e'twecn the' conductor 1 6 Sand the Junctur lof theresi'str'sf 19 "andl, The'fswitch blade- 61 has' connected a shunt circuit |25, |26 between V'ground'-'arid-Ittre juncture of the resistors-'181 and '19. The-switchblade'65 has connected'V ashunt circuit` 123, |24' between g'round #and 'the-"enditerniinalfoffthefe: sistor 82.

Figure 4l2 4shows fthat' diiorent shunt circuits for- Songy have boeuf-provided! between? ground and the resistor 18 'and 19' and betweenground and the 'end terminalfof the Viesistoi' 82.- -It'A will? also be noted that betweenthe conductor vand the juncture of resistor'18'and 8|, two-capacitors ||4 and ||5 are connected in series.

In the Speech position, Figure'133upon Aactuation of push button 5l, aresistor ||6 is con-V nected between the conductor 16 and ground -and a'cap'acitor ||`4 is connectedV between the"con ductor 16 and the common juncture ofrresistor 1S and 8|. From the juncture of resistor 82 with conductor A, there` is provided-a shunt circuit, including the resistor ||2 connected to ground.

In order to further assist those skilled inthe art to follow the teachingsofthe-present invention, typical valuesuoi the components' employed in Figure 2 are -as follows:

Figure 14e-grumman?ulustates changes@ which occur lwh'enf the 'various vpuslr buttons i'ri the speech button 54, haveheen actatdifdrhe' tone control. VvThe curve |133 "shows the reproduce; tion characteristic -wlien'-push butter-ifnhas1 been actuated. Y- Ifnow.' linf a'diitiorilto'this;pishi'yutHV siimstmecyurvsfutl.: mm meneame: volume the level may be decreased byf'ctuatmg i in succession. 'Thus'. thencurve"'|'45:showsl the outputzwh'en `push vbuttons 32h55 and -fllfrhave been actuated.

ss'summmmcfpum umm .It maf-mucubeen actuated,- :successive actuationr :of'the'pmh buttons -32, 83; '34. and 851 will .producelfoutput characteristics 'illustrated Abylcurves |49, 16|; 162 and |58 'as shown in Figure 16.

: xis'surn'inglthat'pushv buttons 51 'and `1li-ofthe tone control have been actuated-,successive actu'- ation of push buttons 32, 33,' 38fand135'wi1l .pme4

duce output curves corresponding to'curvesk Ill, |55, |56 iand |51.. If,:.in.ctuationfof any'ofthe several-buttons 32to'35, push `buttons 12 and l1 havefbeen actuated, the output curves' .would be represented by the curves 156,159, |6| 'andsllL It, 'ofcourse, will be appreciated by those skilled in theffart that the changes indicated between the' setof curves |*54to |51 `and thefcurves |58, |59-,.r=|6| and |62 can be made in any of the preceding characteristic curves Yshown'in Figures 14, 15-and' 16. Therefore, Figure '-14 inva general way, illustrates the efectsproducedby actuation of push buttons 41 and I8 and the curve Vin Figure 1'1 illustrates Ithe eifectfproduced by actuation of the-different push Vbuttons 12 and 14.

From the foregoing-it will vbe appreciated' that in actuating push vbuttons 51, 56; 55 'and 58.111.

thatorder, the low frequency response is reduced andv the high --frequency response vis increased.

v The actuation of the High 'Fidelity push button, H-increases the high frequency response. It will also be-observed that the` least compensation is provided for the very loud reproduction when pushbutton 32 has been actuated. At .other Volumeflevelscompensation is introduced-:for the purpose` previously mentioned. Thus, for the Loud position one compensation circuit-is .produced bythe connection ofV conductor Dbetween the input andan intermediateipoint on .the .voltage divider. For the Medium-,position an additional compensation circuit is produced as shown in Figure 5, whereas for. the-Soft position still another compensation circuitA is introduced as shown in Figure 6. The eiects of these coin-- pensation arrangements are .believed to-be amply apparentby an examination of the output `chanacterist-ics as illustrated -by the curves in Figures 14 i017.V In general, thesecompensation networks l have been` designed so as toV give l approximately the=same volume level foi` each tone' position. The-compensations ,provided for any selected tone position y,are introduced upon actuation of any volume push buttonso as to minimize the-apparent change observedl by Fletcher.

-fWhile ior the purpose'of :illustratingand describing the .present invention a` preferred .embodimenthas been shown-in the drawings.. it is' tolb'e understood that numerous .variationslthereofrrare contemplatedand that.. tor diiiferentf-instaflla'tionsor-fus'e's certain 'variations 1n-there!!!`v 1. A volume control comprising a plurality of v push button switches, a pair of audio input terminals, an impedance network, a plurality of resistors each connected in series and all connected in series with said impedance network across said.

audio input terminals, said impedance network having a pair -of audio output terminals, a plurality of acoustic compensating circuits for selective coupling to said resistors, said compensating circuits each having a diierent frequency re-.4

sponse characteristic, said switches being arranged to couple selected compensating circuits across certain of said resistors when attenuation occurs between said input and output circuits, and

to short circuit certain of said resistors for minii.

mum attenuation between said input and output circuits, said switches being arranged-to produce equal changes in volume level when actuated in progression, and means included in said impedance network and connected in series with said resistors for increasing ordecreasing by equal amounts the volume level as determined by the actuation of any previously selected switch.

2. A volume control comprising a plurality of push button switches of the type where the actuation of one switch releases. the previously actuated switch, an 'attenuation circuit comprising a. plurality of resistors connected in series between audio input and output circuits, a plurality of shunt circuits for selective connection to said resistors,said shunt circuits each having a diierent frequency response characteristic, said switches being connected to said resistors and said shunt circuits to render eiective certain shunt circuits for certain attenuation values and to shunt certain of said resistors for minimum attenuation, said switches being arranged to produce equal changes in volume when actuated in progression, and push button controlled means connected in series with said resistors for increasing or decreasing by equal amounts the volume level as determined by the actuation of any selected one of said first switches, said latter push button controlled means being arranged to be restored to original condition upon the subsequent actuation of one of said rst mentioned push button switches.

3. A volume control system comprising a plurality of push button switches of the type wherein only one button is eiective at a time, a plurality of resistors connected to said switches and in series between audio input and output circuits to produce equal volume level changes when said switches are actuated in progression, said switches being arranged to shunt diierent resistors and to introduce diierent tone compensating circuits to minimize apparent tonal change when volume level is reduced, and push button controlled means connected in series with said resistors for increasing or decreasing by equal amounts the volume level as determined by the actuation of any selected switch thereby to provide intermediate levels of volume.

4. A volume control system comprising a plurality of push button switches of the type wherein only one button is effective at a time, a plurality of resistors connected to said switches and in series between audio input and output circuits to produce equal volume level changes when said switches are actuated in progression, said switches being arranged to shunt different resistors and to introduce diiierent tone compensating circuits to minimize apparent tonal change when volume level is reduced, and push button controlled means connected in series with said resistors for increasing or decreasing by equal amounts the volume level as determined by the actuation of any selected switch thereby tovprovide intermediate levels of volume, said latter push button controlled means being arranged to restore to original condition upon the subsequent actuation of any one of the said iirst mentioned push button switches.

5. A combination volume and tone control system comprising two sets of push button switches wherein only one button in each set is effective at a time, a pair of audio input terminals, an impedance network, a plurality of resistors each connected in series and all connected in series .with said impedance network across said audio input terminals, said impedance network having a pair of audio output terminals, a plurality of compensating circuits having different non-uniform frequency characteristics, circuit connections between certain of said circuits, one set of said switches being operative to short circuit certain of said resistors for progressively increasing in equal steps the output volume level, and means including a pair of push button switches and circuit elements controlled by the last mentioned switches and included in said impedance network for producing intermediate volume level changes.

6. A volume control comprising a plurality of push button switches, a pair of audio input terminals, an impedance network, a plurality of resistors each connected in series and all connected in series with said impedance network across said audio input terminals, said impedance network having a pair of audio output terminals, a plurality of acoustic compensating circuits for selective coupling to said resistors, said compensating circuits each having a differenty frequency response characteristic, said switches being Varranged to couple selected compensating circuits across certain of said resistors when attenuation occurs between said input and output circuits, and to short circuit certain of said resistors for minimum attenuation between said input and output circuits, said switches being arranged to produce similar changes in volume level when actuated in progression, and means included in said impedance network and connected in series with said resistors for increasing or decreasing by like amounts the volume level as determined by the actuation of any previously selected switch.

'7. A push-button-actuated combined tone and volume control device comprising a rsi; resistor, a second resistor, a third resistor, a fourth resistor, and a tone-determining impedance network connected. in series and adapted to be coupled across a source of audio frequency signals, the terminals of said impedance network providing an audio output circuit, a volume controller comprising four depressible buttons, means for assuring the release of the other buttons when any one of said buttons is depressed, switching means responsive to the depression of a first one of said vbuttons (designated Very Loud) for short-circuiting the second and fourth of said resistors, switching means responsive to .the depression of a second one of said buttons (designated Loud) for shortcircuiting the fourth of said resistors-switching means norm-ally short-circuiting the third one of said resistors, a third one of said buttons (designated Medium) being operative solely to releasef the other :.-buttonaA the :iastementioned switching means iieing responsive z to the. .depressionzof the fourth .one o fv .saidfpushbuttonsz (designated fSoftD for removingxthe :short :circuit .onrsaid third resistor. x

8. .A device in accordance :with :claim 27; aeresistance-capacitance'compensatinginetworh and switching. means normai1yconnecting Jsaid-resistance-capacitance network across said.y fourth lresistor. and said impedance, .the last-namedswitch- Aing,means -being responsive r to depressionof the rst one of saidbuttons '('de'signated Very Loud) or the second one of said buttons (designated Loud) to disconnectsaid compensating network from the fiuncti'on of said second. Aand -fthirdtre- 'Sisbort y l9. A device ixr` accordancefwith 'claim y8,--a.nother Vresistance*caiiacitance compensating network, and switching. meansfresponsive todepression Vof the fourth-.one offsaid buttons (designated'fsoft) to connect saidA `other compensating Vnetwork .across .said .third and' .fourth resistors fand" said impedance.

10. -In a -device accordance with Yclonar-"1,2 a tonecontroller inc1udingf-;a-second .set of four push .buttons sof-arranged: `that depression- Aof one causesrelease of the other three, aninputcapacitor. connected to Athe :highspotential r.terminal Y.of said .iirst resistance, three Jcapacitors .in-series, switching meansnormaiiyfconnecting said capacitors across said-mst andsecondresistors Landffsaid input capacitor. said .switching means ,beingmesponsiveto depression of aiirstoneioffsaid push buttons (designated 4rfSymphonyr) to` disconnect said Y three-capacitor. circuit from said: input capacitona second one of saidpushbuttons (designated .Swing) not `disturbing fithat connection, Aswitching..means4 responsive -to`.depression of 4a third one -f-of said ,pushf buttons (designated Songl .to short circuit `one of said three capaci `tors,. and .switching means; responsive to-.depresi sionoi-.alfourth-oneof saidy pushbuttons-(designatedfQSpeech-f) to short circuit.twocfsaidethree capacitors.-

.11. A Adevice in accordance with claim 10,-three independent resistance-capacitor compensating networks, .and awpiuralityV of .switching .means responsive respectively to .depression ofv 'the rst (Symphonyf) secondy (Swing=), and third one ofy said networksacross thesecond, thirdnand fourth` resistors f and-l said impedance network.

12.- A device in accordance Lwith 'c1ai'm:11, .a resistor .compensating network,` andff switching means .-responsive -to.depression. fof the` fourth (-Speech push .button tofconnect--saidz resistor compensating network. across @the input aiof ,f the device.

13. A. device.- in accordance .withrclaimgllfthree other.- independent resistance-.capacitance l come pensating networks; another resistor-compensat# ing,4 networkand a plurality. ofswitchingm'eans responsive respectivelyr to: depression.. of 'the iii-st (lrSymphonyv), second (Swing third (-fvSong' .and fourth (Speech..) push buttons to -include a..-se1ected` `one Yof said'. yother .compensatingnetworks in said'impedance-.network 14. AA -deviceA in accordance vwith .ciaim`13, and a fifth push` button (designated .High .Fide1ity) inciudedin saiditone controller for releasing. al1 of the .-rst founpush buttons Voffrsaid controller.'

l.15.. A device in. accordance withc1'aim-14, an amplifier coupled. to -said .audio :output i. circuit,` a shunt capacitor; a sixth. independent push button (designated Normalirand switchingineans 'i12 responsiveitofdepressionfof said six'thpshihutwn to encircuit said shunt capacitor with said amplifier. Y

16. A device in accordancewith .claim r["in 5 which the impedance network comprises a-irst series4 :capacitorshunt resistor :nltersectionr iii th and-.sixth push buttons in the volume controller (designated and a second series'resistor-shunt resistor ffilter section, a-thirdzsmes -resistor-.shunt resistor iter section; switching means normailymonnecting the secondniterfsec- .tion r in cascade fwith` andA 'aheadnof the :rst'xaid -swtiching meanszbeing rcsponsiveftofthe` deprission ofathe tlfthoisaid pushibuttons'( to remove thez second diluer ..fromfsaiidaimpedan'ce network,` and switchingzmeans responsive Ytoi-the depression of the sixthotfsaidpushibuttons (designatedff-Jf) .toninterposin'gzthethirdsectim between the :rst andfsecondnitersectionaaeoch .20 of f said "ffifth :and push` buttons :having mo effect on the :rst four/but beinglrcicascdby depressionofany"Oneofsaidioun' 17 vInra push-button actuated '.c'ombinedtone and volume control 1 device; four. resistors adapted toben-coupled across 'afsource Foff'audio frequency signals, .the terminals 'offsaid :impedance 'providing fan. audio'A output ci'icuit..V Sofi-tone controller includingaiset artour pushbutwns so arranged .that -depressionnzuf one'causes reiemo! the other three; an input vcapacitor '.nnecdto the "highepotential cte'rminnizzofthe: mist. realtor. three :capacitors in zsericx; Viswitchinif: moans fmtmally connecting. saidV capacitorsacross the iint Yand zsecond -resistors and :said' rinpiitcapwitr. vsaid switching means :beingresponstve .tc'dlpmsion 'of'v a iirst Yone of .said :push` buttons-.(116318- nated Symphony.')' to lzdisconnect 'i said: threocapacitor circuit from 'fsaiii-A 'finput *capacitan .n

'.U .second oneAA of said ipush buttons: (designated 5 fourth resistances and "said impedance.

19..A device vin accordance with claim'i, `a resistor compensating network, andv switching means responsive to depression ot the^fourth (-S`pecchf)pushbuttony to :connect sa1d^resistor G0 compensatingnetwork 'across the input ofithe device.'V

120'. A deviceinfaccordance with -claim '19; three other independent resistancecapacitance coniL pensating networks, another resistor compensating network, and a1 plurality of switchitisr means Yresponsive respectively Ito" depression of the rst (Symphony), second(Swing,). 'third (Song), and fourth (Speechv) push huttons'to include alselected one 'of-A said timex-compensating networks in said impedance.

13 amplier coupled to said audio output circuit, a shunt capacitor, a sixth push button (designated Normal), and switching means responsive to depression of said sixth push button to shunt encircuit said capacitor with said amplifier.

23. A device in accordance with claim 17 in which the impedance network comprises a first series capacitor-shunt resistor filter section, a pair of push buttons in the volume controller (designated and a second series resistor-shunt resistor filter section, a third series resistor-shunt resistor iilter section, switching means normally connecting the second filter sec--l tion in cascade with and ahead of the first, said switching means being responsive to the depression of one of said push buttons (designated to remove the second filter section from said impedance network, and switching means responsive to the depression of the other of said push buttons REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,864,527 Castner June 28, 1932 2,101,832 Barton Dec. 14, 1937 2,511,924 Lee June 20, 1950 5 FOREIGN PATENTS Number Country Date 394,712 Great Britain July 3, 1933 

